Hello in new at growing hydrangeas what should i do to take care of my newly bought quart size plants if they are delivered before the weather is right too plant outside.Thank you.
An answer to best help you depends on the variables. There are a few "unknowns" that make it difficult to give you good advice.
From your post I am assuming that you mail ordered them and they will be delivered, already planted in quart pots.
So generally speaking:
If they are leafed out when they arrive, and you are in a growing zone that is still below freezing, you should protect them. If you are in zone 6 or warmer, an unheated garage would be fine until weather is milder.
Watering them while in a holding pattern indoors (in an unknown potting medium) is tricky and should be carefully done. They will need moisture but if kept too wet, or the medium holds too much water, they can rot.
Plant them about 2-3 weeks after your average date of last frost in Spring, all the while keeping them comfy and moist as Deb said above.